Gentilissimi.
Ho fatto tutto quello che mi avete suggerito e il maledetto non si è più ripresentato.
Vi posto il nuovo log:

Logfile of HijackThis v1.99.1
Scan saved at 17.06.14, on 29/06/2006
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\spoolsv.exe
C:\Programmi\ewido anti-spyware 4.0\guard.exe
C:\Programmi\File comuni\Microsoft Shared\VS7DEBUG\MDM.EXE
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\wscntfy.exe
C:\windows\system\hpsysdrv.exe
C:\WINDOWS\system32\hphmon06.exe
C:\HP\KBD\KBD.EXE
C:\Programmi\iTunes\iTunesHelper.exe
C:\WINDOWS\system32\keyhook.exe
C:\WINDOWS\AGRSMMSG.exe
C:\Programmi\Real\RealPlayer\RealPlay.exe
C:\Programmi\ewido anti-spyware 4.0\ewido.exe
C:\Programmi\Java\jre1.5.0_07\bin\jusched.exe
C:\WINDOWS\system32\ctfmon.exe
C:\Programmi\iPod\bin\iPodService.exe
C:\Programmi\Messenger\msmsgs.exe
C:\Programmi\Samsung\Digimax Viewer 2.1\STImgBrowser.exe
C:\Programmi\HP\Digital Imaging\bin\hpqtra08.exe
C:\Programmi\InterVideo\Common\Bin\WinCinemaMgr.ex e
C:\WINDOWS\system32\wuauclt.exe
C:\Programmi\Hijackthis\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = about:blank
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://ie.redirect.hp.com/svs/rdr?TY...ion&pf=desktop
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://ie.redirect.hp.com/svs/rdr?TY...ion&pf=desktop
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = about:blank
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://ie.redirect.hp.com/svs/rdr?TY...ion&pf=desktop
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = http://ie.redirect.hp.com/svs/rdr?TY...ion&pf=desktop
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://ie.redirect.hp.com/svs/rdr?TY...ion&pf=desktop
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Window Title = Microsoft Internet Explorer
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
O2 - BHO: AcroIEHlprObj Class - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Programmi\Adobe\Acrobat 6.0\Reader\ActiveX\AcroIEHelper.dll
O3 - Toolbar: Vista HP - {B2847E28-5D7D-4DEB-8B67-05D28BCF79F5} - c:\Programmi\HP\Digital Imaging\bin\HPDTLK02.dll
O3 - Toolbar: Easy-WebPrint - {327C2873-E90D-4c37-AA9D-10AC9BABA46C} - C:\Programmi\Canon\Easy-WebPrint\Toolband.dll
O4 - HKLM\..\Run: [hpsysdrv] c:\windows\system\hpsysdrv.exe
O4 - HKLM\..\Run: [HPHUPD06] c:\Programmi\HP\{AAC4FC36-8F89-4587-8DD3-EBC57C83374D}\hphupd06.exe
O4 - HKLM\..\Run: [HPHmon06] C:\WINDOWS\system32\hphmon06.exe
O4 - HKLM\..\Run: [KBD] C:\HP\KBD\KBD.EXE
O4 - HKLM\..\Run: [iTunesHelper] C:\Programmi\iTunes\iTunesHelper.exe
O4 - HKLM\..\Run: [Recguard] C:\WINDOWS\SMINST\RECGUARD.EXE
O4 - HKLM\..\Run: [VTTimer] VTTimer.exe
O4 - HKLM\..\Run: [SiS Windows KeyHook] C:\WINDOWS\system32\keyhook.exe
O4 - HKLM\..\Run: [AGRSMMSG] AGRSMMSG.exe
O4 - HKLM\..\Run: [PS2] C:\WINDOWS\system32\ps2.exe
O4 - HKLM\..\Run: [Easy-PrintToolBox] C:\Programmi\Canon\Easy-PrintToolBox\BJPSMAIN.EXE /logon
O4 - HKLM\..\Run: [RealTray] C:\Programmi\Real\RealPlayer\RealPlay.exe SYSTEMBOOTHIDEPLAYER
O4 - HKLM\..\Run: [PinnacleDriverCheck] C:\WINDOWS\system32\PSDrvCheck.exe -CheckReg
O4 - HKLM\..\Run: [AtiPanel] C:\WINDOWS\atip.exe
O4 - HKLM\..\Run: [!ewido] "C:\Programmi\ewido anti-spyware 4.0\ewido.exe" /minimized
O4 - HKLM\..\Run: [SunJavaUpdateSched] C:\Programmi\Java\jre1.5.0_07\bin\jusched.exe
O4 - HKCU\..\Run: [ctfmon.exe] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [MSMSGS] "C:\Programmi\Messenger\msmsgs.exe" /background
O4 - Global Startup: Adobe Gamma Loader.exe.lnk = C:\Programmi\File comuni\Adobe\Calibration\Adobe Gamma Loader.exe
O4 - Global Startup: Digimax Viewer 2.1.lnk = ?
O4 - Global Startup: HP Digital Imaging Monitor.lnk = C:\Programmi\HP\Digital Imaging\bin\hpqtra08.exe
O4 - Global Startup: InterVideo WinCinema Manager.lnk = C:\Programmi\InterVideo\Common\Bin\WinCinemaMgr.ex e
O8 - Extra context menu item: &Point&&Go - C:\Programmi\File comuni\Expert System\PGPlatform\PGPlatform.htm
O8 - Extra context menu item: Aggiungi all'elenco di stampa Easy-WebPrint - res://C:\Programmi\Canon\Easy-WebPrint\Resource.dll/RC_AddToList.html
O8 - Extra context menu item: Anteprima Easy-WebPrint - res://C:\Programmi\Canon\Easy-WebPrint\Resource.dll/RC_Preview.html
O8 - Extra context menu item: E&sporta in Microsoft Excel - res://C:\PROGRA~1\MICROS~3\OFFICE11\EXCEL.EXE/3000
O8 - Extra context menu item: Stampa ad alta velocità Easy-WebPrint - res://C:\Programmi\Canon\Easy-WebPrint\Resource.dll/RC_HSPrint.html
O8 - Extra context menu item: Stampa Easy-WebPrint - res://C:\Programmi\Canon\Easy-WebPrint\Resource.dll/RC_Print.html
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Programmi\Java\jre1.5.0_07\bin\npjpi150_07.dll
O9 - Extra 'Tools' menuitem: Sun Java Console - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Programmi\Java\jre1.5.0_07\bin\npjpi150_07.dll
O9 - Extra button: Ricerche - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~3\OFFICE11\REFIEBAR.DLL
O9 - Extra button: Real.com - {CD67F990-D8E9-11d2-98FE-00C0F0318AFE} - C:\WINDOWS\system32\Shdocvw.dll
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe
O14 - IERESET.INF: START_PAGE_URL=http://www.virgilio.it/free
O20 - Winlogon Notify: igfxcui - C:\WINDOWS\SYSTEM32\igfxsrvc.dll
O23 - Service: Ati HotKey Poller - Unknown owner - C:\WINDOWS\system32\Ati2evxx.exe
O23 - Service: ewido anti-spyware 4.0 guard - Anti-Malware Development a.s. - C:\Programmi\ewido anti-spyware 4.0\guard.exe
O23 - Service: Servizio iPod (iPodService) - Apple Computer, Inc. - C:\Programmi\iPod\bin\iPodService.exe

Ancora grazie
Alberto